Although not exclusively, the present invention is especially well adapted for aircrafts, the engines of which are provided with thrust inverters.
It is known that modern aircrafts, including transport civil aircrafts, are provided with engines individually controlled by throttle control levers. The latter could occupy several positions, each associated with an engine speed generating a determined thrust, amongst which an idling position and a take-off position. The engines of such aircrafts are frequently provided with thrust inverters, so that the control levers are further able to occupy a thrust inversion position, allowing for the activation of the thrust inverters, being generally arranged so that the idling position is interposed between the thrust inversion position and the take-off position.
Upon landing of an aircraft, before the wheels touch the runway, pilots cut off the thrust of the engines or take over the regulation that was automatic (associated with the self-lever mode) through bringing or taking the control levers in the idling position. Then, they are able to activate the thrust inverters, bringing the control levers in the thrust inversion position so as to perform a braking through a thrust inversion. When such braking is achieved, pilots deactivate the thrust inverters bringing the control levers in the idling position, from the thrust inversion position.
Technological developments provided to managing aircraft control levers (including, removing the motorization of the levers) have led to the introduction of a monitoring based on the position of said levers upon landings, so as to remind the crew to put the control levers in an idling position during flaring upon landing and before the wheel touch. Such a monitoring is generally performed by a flight warning calculator on board the aircrafts.
Such a monitoring is characterized by the single and systematic emission of a speech reminding indication when the altitude of the aircraft is at the most equal to an altitude threshold (10 or 20 feet depending on the landing mode), so as to remind pilots to bring the throttle control levers in the idling position. Such a reminding indication has the shape of a speech synthesis, optionally preceded or not by a announcement of the usual altitude of the aircraft. It is routinely emitted upon each flight of the aircraft, whatever the position of the control levers.
Moreover, upon a landing, when the altitude of the aircraft is below the altitude threshold, this same reminding indication, is emitted at regular intervals as long as at least one of the three following conditions is not met:                one of the control levers occupies the thrust inversion position;        the control levers occupy the take-off position;        the control levers occupy the idling position.        
However, the above mentioned monitoring does not take into account some cases of lever dissymmetry able to generate critical situations, such as going off a runway as a result of a position dissymmetry for the control levers upon a landing.
Indeed, after the wheels have touched the ground, upon bringing the control levers in the idling position or in the thrust inversion position, at least one control lever could remain in a position ahead of the idling position, i.e. associated with a higher engine speed than the idling speed, generating a first case of dissymmetry in the position of the control levers.
When such a dissymmetric position of the control levers is detected by the warning calculator upon a landing, the latter triggers a red warning comprising the steps consisting of:                emitting a sound warning in the shape of a disharmonious and repetitive chime sound (or CRC warning for <<Continuous Repetitive Chime>>);        triggering a light on a flight control interface; and        displaying a text message on an engine warning screen in the cockpit of the aircraft.        
However, the warning calculator does not take into consideration, upon landing, a second case of position dissymmetry for the control levers resulting from the latter being inappropriately handled. More precisely, after the wheels have touched the runway, upon the deactivation of the thrust inverters (i.e. when the control levers switch from the thrust inversion position to the idling position), at least one control lever can be depressed inadvertently in a position ahead of the idling position, corresponding to an engine speed higher than the idling speed.
Such a position dissymmetry for the control levers generates a thrust dissymmetry of the aircraft engines, upon the ground running phase (following a braking through thrust inversion), able to cause the aircraft to go off the runway.